Refrigerating method and device

ABSTRACT

The invention relates especially to a refrigerating device comprising a pressure-resistant container (1) furnished with an adsorbent material (2), which device furthermore comprises an adjustably set valve (7) whose passage communicates, on the one hand, with the inside of the container and, on the other hand, with the outside, and means (5, 6) for bringing said container temporarily into communication with a pressurized source (10, 11) of gas which can be adsorbed by said adsorbent material. 
     Use in refrigerated clothing or portable refrigerators.

FIELD OF THE INVENTION

The invention relates to a refrigerating method and a refrigeratingdevice.

BACKGROUND OF THE INVENTION

There is a need for a refrigerating device which is lightweight,portable and nonelectric in various fields, such as portablerefrigerators, refrigerated clothing, etc.

It has already been proposed to produce cold by the adsorption of CO₂ onan adsorbent material and then desorption of the adsorbed gas.EP-A-0,523,849 describes a device, based on this principle, consistingof a cylinder which contains an adsorbent material and a compressiblegas (such as CO₂) and of a piston actuated by a compressor in order tocompress the gas so as to make it be adsorbed by the adsorbent material.When the piston is retracted, the gas is desorbed and produces cold. Bysuccessive compressions and decompressions, a cold region and a hotregion are created in the mass of adsorbent material. Means (fins) areprovided in order to cool the hot region and to convey the frigoriesfrom the cold region to an enclosure to be refrigerated.

This device, which requires a compressor in order to actuate the piston,suffers from being heavy and bulky. This is manifestly not arefrigerating device designed to be lightweight and portable.

Likewise, the Applicant Company claims, in French Patent Application No.93/09348 filed on Jul. 29, 1993, a device for producing cold byadsorption/desorption of CO₂, comprising at least one enclosurefurnished with an adsorbent solid material, wherein this adsorbentmaterial comprises activated-carbon fibers or an activated charcoal andhas a specific surface area of at least 700 m² /g and an externalspecific surface area of at least 0.005 m² /g. The aforementionedapplication also specifically describes refrigerating systems of thesimple effect type or of the resorption type which require the use oftwo interconnected enclosures and of heating means and which thereforedo not lend themselves to producing lightweight and portable systems.

The need for a method of producing cold, which can be used inlightweight and portable devices, has therefore not hitherto been met.

The invention relates to a novel method of producing cold by adsorptionof a pressurized gas, which can be adsorbed by an adsorbent materialheld in a container, and then desorption of said gas, wherein the gas isdesorbed under a controlled pressure greater than atmospheric pressureand wherein the desorbed gas is discharged to atmosphere or captured ina trap.

Contrary to the prior methods, the desorbed gas is neither reused nortransferred to another enclosure in order to be subsequently recycled,and this feature allows refrigerating devices to be produced which aresimple, lightweight and portable.

By "controlled pressure" is meant a constant or substantially constantpressure or a variable pressure whose variation is regulated dependingon a given parameter, especially the temperature of the device used toimplement said method or of the article or enclosure cooled by the coldgenerated by means of a device implementing the present method.

The desorption of the gas is carried out under a controlled pressuregreater than atmospheric pressure so as to prevent air from being ableto get back into the container holding the adsorbent material.

The present invention also relates to a refrigerating device which islightweight, portable and simple to produce.

More particularly, the invention relates to a refrigerating devicecomprising a pressure-resistant container furnished with an adsorbentmaterial, which device furthermore comprises an adjustably set valvewhose passage communicates, on the one hand, with the inside of thecontainer and, on the other hand, with the outside, and means forbringing said container temporarily into communication with apressurized source of gas which can be adsorbed by said adsorbentmaterial.

According to one particular embodiment, said means consist of a two-partquick-action coupling of the self-sealing type, one of the parts ofwhich is fixed to the container and the other part of which is fixed tothe valve, so that the container can be disconnected from the valve andconnected to said pressurized source in order to be filled withadsorbable gas.

As a variant, a percussion-type recharging system could also be used,that is to say one of the type comprising a needle whose channel isconnected via a valve or the like to the chamber delimited by thecontainer and a membrane which is provided on a pressurized absorbablegas source and which is transpierced by the needle when it is desired to"recharge" the container.

Preferably, the adsorbable gas is carbon dioxide (CO₂) and the outlet ofthe valve emerges directly into the atmosphere.

As a variant, the adsorbable gas could be ammonia (NH₃), in which casethe outlet of the valve would emerge into a water trap intended toabsorb the desorbed ammonia and to prevent or greatly minimize itsrelease into the atmosphere.

It is also possible to envisage using a system involving severaladsorbed substances so as to base the production of cold on two or moreenthalpic systems (co-adsorption) instead of one. An example of such asystem is the carbon dioxide/water system.

The container of the device of the invention must be capable of holdingthe pressure of the adsorbable gas introduced. For example, thecontainer may be made of a metal such as steel or made of a compositematerial which is a good heat conductor, for example a polymericmaterial filled with metal fibers.

Advantageously, the container has a substantially cylindrical elongateshape in order to provide a large heat exchange area.

Preferably too, in order to guarantee good access for the adsorbable gasto the entire mass of adsorbent material filling the container, theinlet orifice for the adsorbable gas is provided at one end of thecontainer and an access path is provided for the gas by placing a smalltube which is perforated or made of mesh in the container, extendingfrom the inlet orifice for the adsorbable gas right to the opposite endof the container.

The adsorbent material may be of any kind. Examples of preferredabsorbent materials are activated-carbon fibers having a specificsurface area of at least 700 m² /g, preferably at least 1000 m² /g, andhaving an external surface area of at least 0.2 m² /g, such as thefibers sold under the name AD'ALL by the Japanese company OSAKA GAS Co.Ltd. or under the names KF (or K-Filter) and AF by the Japanese companyTOYOBO Co. Ltd., Osaka, Japan, activated charcoals having a specificsurface area of at least 700 m² /g, preferably at least 1000 m² /g, andhaving an external specific surface area of at least 0.005 m² /g,preferably at least 0.02 m² /g, such as the charcoals sold under thename PICACTIF, reference TA 60 or TA 90, by the company PICA, 92309Levallois, France.

Advantageously, it is possible to mix a material which is a good heatconductor with the adsorbent material so as to improve the heat exchangewithin said adsorbent material and between the latter and the wall ofthe container. A preferred example of such a material which is a goodheat conductor is recompressed expanded graphite. Expanded graphite isavailable from the company LE CARBONE-LORRAINE.

The mixture of recompressed expanded graphite and the adsorbent materialmay be made by firstly compressing expanded graphite, for example in acylinder by means of a piston, and then by impregnating the porous blockof recompressed expanded graphite obtained with a suspension of fineparticles of adsorbent material in a liquid medium (water or anotherliquid) which is removed after impregnation, for example by controlledheating.

Self-sealing quick-action couplings are well-known articles marketed,for example, by the company STAUBLI, 74210 Faverges, France, as areadjustably set valves, for example those set by means of an adjustablecompression spring, which may be obtained, for example, from the NUPROCOMPANY, Willoughby, Ohio (U.S.A.).

The operation of the device of the invention is very simple, itsuffices, after disconnecting the valve, to connect the container to anadsorbable gas source, such as a carbon dioxide cylinder fitted with apressure-relief valve, until the adsorbent material has adsorbed thedesired quantity of adsorbable gas, which may be determined simply byweighing. The time necessary to recharge depends on various parameters,but a suitable time may easily be determined once and for all by asimple routine experiment. Recharging usually requires only a fewminutes. Likewise, most producers of adsorbent materials supply chartsenabling the volume of adsorbed gas to be determined for a givenpressure and temperature pair.

The recharging pressure is solely limited by the mechanical strength ofthe container of the present device and by the available adsorbable gassource. By way of indication, in the case of CO₂ as adsorbable gas, therecharging pressure could range from 2 to 72 bar and higher (at anambient temperature of 30° C.). The higher the gas pressure in thecontainer, the greater the amount of cold which can be produced by agiven device.

Having completed the recharging, the device is disconnected from thesource and the valve and container are reconnected, the valve being setto an opening pressure greater than the internal pressure existing inthe container in order to avoid any inadvertent gas leak.

When it is desired to produce cold using the device, it suffices to setthe valve to an opening pressure less than the internal pressureexisting in the container so that desorption of the adsorbed gas occursand generates frigories which cool the wall of the container. The coldproduced may be exchanged with air or a fluid in any suitable manner.For example, a stream of air or liquid to be cooled may be made to flowaround the container using a fan, pump or similar device. Heat exchangemay be increased by providing heat-exchange means known per se, such asmetal fins or the like, around the container.

The device of the invention is useful in all fields of applicationrequiring a lightweight and autonomous source of cold. Mention may bemade, purely by way of indication, of refrigerated clothing and portablerefrigerators.

The description which follows, given with reference to the drawings,will make the invention clearly understood.

FIG. 1 is a diagrammatic view of a refrigerating device according to theinvention; and

FIG. 2 is a diagrammatic view illustrating the recharging of the deviceof FIG. 1.

The refrigerating device of the invention comprises a cylindricalstainless-steel container 1 having a length of 165 mm, an internaldiameter of 30.5 mm and an external diameter of 33.7 mm, furnished witha mixture 2 of 34.7 g of PICACTIF TA 90 activated charcoal and 18.7 g ofexpanded graphite, initially having a density of 0.04, which has beenrecompressed.

Provided at the center of the mass of adsorbent material is a smallcylinder 3 formed by a fine-celled mesh extending from one end of thecontainer to the other and intended to provide easy access for theadsorbable gas to all parts of the adsorbent material. An orifice 4 isprovided at one of the ends of the cylinder and the female part 5 of aself-sealing quick-action coupling is welded around this orifice. Themale part 6 of the quick-action coupling is itself welded to a valve 7which can be adjustably set by means of a knob 8. In FIG. 1, the malepart and the female part of the coupling are shown in a coupledposition.

By way of indication, the coupling used, supplied by the companySTAUBLI, comprised a 5.5 SPM coupling (female part) and a 5.5 SPM endfitting (male part). The adjustably set valve (which can be set between0 and 15 bar), of the 316 L type, came from the American company NUPRO.

FIG. 2 illustrates diagrammatically the recharging of the device of FIG.1.

After disconnecting the two parts 5 and 6 of the quick-action coupling,the container 1 is connected to the pressure-relief valve 10 of a bottle11 of pressurized adsorbable gas (for example CO₂) by coupling thefemale part 5, fastened to the container 1, to a male quick-actioncoupling part 12, similar to the male part 6, connected to thepressure-relief valve 10. All that then requires to be done is to openthe pressure-relief valve in order for recharging to take place. Oncerecharging has been completed, the pressure-relief valve is closed, theparts 5 and 12 are disconnected and, after closing the valve 7, theparts 5 and 6 are reconnected.

Given below, by way of nonlimiting example, are the results of two testscarried out using the device of FIG. 1, the first in constant-pressureoperating mode and the second in variable-pressure operating mode.

EXAMPLE 1 Constant-Pressure Mode

The device was charged with CO₂ until the internal pressure in theadsorber was 8.8 bar for an external temperature of 13° C.

The setting (opening pressure) of the valve was adjusted to 1.3 bar. Thetemperatures T₁ and T₂ were measured at two different points on the wallof the container, one (T₁) located near that end of the container wherethe orifice 4 of the container is and the other (T₂) located near theother end of the container 1.

The results are given in the following table. The pressure p in thecontainer was periodically measured using a pressure gage connecteddirectly to the container.

    ______________________________________                                        t(min)    T.sub.1       T.sub.2                                                                             p                                               ______________________________________                                        0         16            13    8.77                                            2         2             3     1.31                                            2.5       3             1     1.29                                            3         1             0     1.26                                            3.5       1             0     1.25                                            4         1             0     1.25                                            4.5       1             0     1.25                                            5         2             0     1.25                                            5.5       2             1     1.25                                            6         2             1     1.25                                            6.5       2             1     1.25                                            7         3             2     1.26                                            7.5       3             2     1.26                                            8         3             2     1.26                                            8.5       4             3     1.26                                            9.5       4             3     1.29                                            10        5             4     1.3                                             10.5      5             4     1.31                                            11        5             4     1.32                                            12        6             5     1.34                                            13        6             5     1.35                                            14        7             6     1.35                                            15        7             6     1.32                                            16        7             6     1.35                                            17        7             6     1.36*                                           18        8             7     1.37                                            19        8             7     1.38                                            20        8             7     1.39                                            21        8             7     1.4                                             24        9             12    1.43                                            25        10            12    1.44                                            50        12            11    1.51                                            85        13            11    1.58                                            ______________________________________                                         *Closing of the valve                                                    

EXAMPLE 2 Variable-Pressure Mode

Initially, the device was charged with CO₂ until the internal pressurein the adsorber was 8.2 bar for an ambient temperature of 12° C.

In this test, the setting of the valve was adjusted manually dependingon the temperature of the wall so as to maintain the temperature of thewall close to 6°-7° C.

The pressure p and the temperatures T₁ and T₂ were measured as describedin Example 1. The results obtained are given in the table below:

    ______________________________________                                        t(min)      p      T.sub.1     T.sub.2                                                                           T.sub.amb                                  ______________________________________                                        0           7.86   12          12  12                                         2           4.55   8           8   12                                         2.5         4.51   7.5         8   12                                         3           4.52   7.8         8   12                                         3.5         4.52   8           8   12                                         4           4.51   8           8   12                                         4.5         4.51   8           8   12                                         5           4.51   8           8   12                                         6           4.51   8           8   12                                         6.5         4.35   7           7   12                                         9           3.18   6           7   12                                         9.5         3.17   6           7   12                                         10          3.17   6           7   12                                         11          3.17   6           7   11                                         12          3.17   6           7   11                                         13          2.85   6           7   11                                         14          2.77   6           7   11                                         15          2.72   6           7   11                                         16          2.7    6           7   11                                         17          2.68   6           7   11                                         18          2.68   6           7   11                                         19.5        2.3    6           7   11                                         20          2.16   5           6   11                                         21          2.07   5           6   11                                         22          2.01   5           6   11                                         24          1.97   5           6   11                                         25          1.96   5           6   11                                         26          1.94   5           6   11                                         27          1.55   5           6   11                                         28          1.46   4           5   11                                         29          1.4    4           5   11                                         30          1.37   4           5   11                                         32          1.31   4           5   11                                         35          1.26   4           6   11                                         36          1.29   5           6   11                                         ______________________________________                                    

By comparing the results obtained in Examples 1 and 2, it may be seenthat the constant-pressure mode enables relatively strong cooling to beobtained for a relatively short time, while the variable-pressure modeenables more modest cooling to be obtained but for a longer period.

It goes without saying that the embodiment described is merely anexample and that it could be modified, especially by substitution oftechnical equivalents without thereby departing from the scope of theinvention.

We claim:
 1. A method for producing cold, comprising:adsorbingpressurized carbon dioxide in an adsorbent material held in a container,and then desorbing said carbon dioxide under a controlled pressuregreater than atmospheric pressure, the desorbed carbon dioxide beingdischarged to atmosphere and said adsorbent material being selected fromat least one member of the group consisting of activated carbon fibersand activated charcoals.
 2. The method as claimed in claim 1, whereincarbon dioxide is desorbed at a substantially constant pressure.
 3. Themethod as claimed in claim 1, wherein carbon dioxide is desorbed at avariable pressure, the variation of which is regulated as a function ofa given temperature.
 4. The method as claimed in claim 1, wherein saidadsorbent material is mixed with a material which is a good heatconductor.
 5. The method as claimed in claim 4, wherein saidheat-conductor material is recompressed expanded graphite.
 6. The methodas claimed in claim 1, wherein the carbon dioxide pressure is at least 2bars.
 7. The method as claimed in claim 1, wherein the method steps arecaused to be performed without electrical power.
 8. The method asclaimed in claim 1, wherein said adsorbent material in said containerconsists essentially of said adsorbent material selected from at leastone member of the group consisting of activated carbon fibers andactivated charcoals.
 9. A refrigerating device comprising apressure-resistant container furnished with an adsorbent materialselected from at least one member of the group consisting of activatedcarbon fibers and activated charcoals, which device further comprises anadjustably set valve whose passage communicates, on the one hand, withthe inside of the container and, on the other hand, with the outside,said device further comprising means for bringing said containertemporarily into communication with a pressurized source of carbondioxide.
 10. The device as claimed in claim 9, wherein said means forbringing consists of a two-part quick-action coupling of theself-sealing type, one of the parts of which is fixed to the containerand the other part is fixed to the valve, so that the container can bedisconnected from the valve and connected to said pressurized source inorder to be filled with carbon dioxide.
 11. The device as claimed inclaim 9, which further comprises a small tube which is perforated ormade of mesh, extending from an inlet orifice for carbon dioxide,provided at one end of the container, to the opposite end of thecontainer.
 12. The device as claimed in claim 9, wherein said adsorbentmaterial is mixed with a material which is a good heat conductor. 13.The device as claimed in claim 12, wherein said heat-conductor materialis recompressed expanded graphite.
 14. The device as claimed in claim 9,wherein the pressurized source of carbon dioxide is a pressurized sourceof carbon dioxide having a pressure of at least 2 bar.
 15. The device asclaimed in claim 9, having an absence of an electrical power supply. 16.The device as claimed in claim 9, wherein adsorbent material of saiddevice consists essentially of said adsorbent member selected from atleast one member of the group consisting of activated carbon fibers andactivated charcoals.